Learn PHP Web Application Development: Complete Guide (2023)

PHP is a popular web development language that has been around for more than two decades. It is widely used to create dynamic web applications and is an essential skill for aspiring web developers. Learning PHP web application development can open up numerous opportunities for individuals looking to build a career in web development.

Learn to Build Applications with PHP Web Development

In this article, readers will learn about PHP web application development basics, including its syntax, functions, and features. They will also gain an understanding of how to use PHP to create dynamic web pages, manage databases, and interact with users.

By the end of the article, readers will have a solid foundation in PHP web application development and be able to create their web applications.

Article Highlights

PHP is a widely used web development language for creating dynamic web applications and popular platforms like WordPress, Facebook, and Wikipedia.
Variables in PHP store values for access and manipulation throughout the program. They are case-sensitive, with $name and $Name being distinct.
PHP supports multiple data types, including strings, integers, floats, booleans, and arrays.
In PHP, we use operators for arithmetic calculations, value comparisons, combining multiple conditions, and assigning values to variables.
PHP provides control structures to manage the flow of code execution. This includes conditional statements (if and switch) and loops (for, foreach, while, and do-while).
Functions, both built-in and user-defined, are crucial in PHP programming.
PHP arrays, key components of PHP programming, comprise indexed arrays, associative arrays, and multidimensional arrays, each offering unique advantages and functions for data organization and manipulation.
Multidimensional arrays in PHP can hold other arrays, enabling the creation of complex data structures.
PHP database interaction requires a connection setup via mysqli_connect(), followed by data retrieval, insertion, updating, or deletion with SQL queries executed by the mysqli_query() function.
PHP web application development includes HTTP request methods for server interaction, form handling for user data submission, and cookies and sessions for client- and server-side data storage.
File handling in PHP is accomplished through functions such as fopen(), fwrite(), and fclose(), permitting the reading and writing of data to server files, along with the ability to manipulate directories.

Why Learn PHP

PHP is a popular server-side scripting language used for web development. It is free, open-source, and widely supported by web servers, making it a popular choice for building dynamic websites and web applications.

Here are a few reasons why learning PHP can be beneficial:

Wide Usage

PHP is used by millions of websites, including popular platforms like WordPress, Facebook, and Wikipedia. This means there is a high demand for PHP developers, and learning PHP can open up many job opportunities.

Easy to Learn

PHP is known for its simplicity and ease of use, making it an ideal language for beginners. The syntax is straightforward, and many online resources and tutorials are available to help you in learning PHP.

Versatility

We can use PHP for various tasks, from simple scripts to complex web applications. We can integrate it with other technologies, such as databases and web frameworks, to create powerful and dynamic websites.

Cost-effective

Since PHP is open-source with no licensing fees when using it. This makes it a cost-effective option for businesses and individuals looking to create web applications on a budget.

Community Support

PHP has a large and active community of developers who contribute to its development and provide support through forums, online communities, and user groups. This means that there are many resources available for learning and troubleshooting PHP.

Learning PHP can be a valuable skill for anyone who has great a interest in web development. Its wide usage, ease of use, versatility, cost-effectiveness, and community support make it a popular choice for building dynamic websites and web applications.

Basics of PHP

Variables

In PHP, we use variables store values that we can access and manipulate throughout the program. A variable is created by assigning a value to a name using the assignment operator (=). PHP variables are case-sensitive, meaning that $name and $Name are two different variables.

$name = "John";
$age = 30;

Data Types

PHP supports several data types, including strings, integers, floats, booleans, and arrays. A string is a sequence of characters enclosed in quotes. Integers are whole numbers, while floats are numbers with decimal points. Booleans can have either a true or false value and we use arrays to store multiple values in a single variable.

Click here to check out our detailed article on the topic of data structures.

$name = "John"; //string
$age = 30; //integer
$height = 5.7; //float
$isMale = true; //boolean
$fruits = array("apple", "banana", "orange"); //array

Operators

PHP supports several operators, including arithmetic, comparison, logical, and assignment operators. In PHP, we use the Arithmetic operators to perform mathematical operations, and comparison operators are used to compare values. And we use Logical operators to combine multiple conditions and assignment operators to assign values to variables.

$x = 10;
$y = 5;

//arithmetic operators
echo $x + $y; //15
echo $x - $y; //5
echo $x * $y; //50
echo $x / $y; //2

//comparison operators
echo $x == $y; //false
echo $x != $y; //true
echo $x > $y; //true
echo $x < $y; //false

//logical operators
echo $x > 0 && $y > 0; //true
echo $x > 0 || $y < 0; //true

//assignment operators
$x += $y; //$x is now 15

Control Structures

Control structures are an essential part of any programming language. They allow developers to control the flow of code execution based on certain conditions. PHP provides a wide range of control structures that we can use to create complex applications.

In this section, we will discuss two of PHP’s most important control structures: conditional statements and loops.

Conditional Statements

In PHP, we use Conditional statements to execute code based on certain conditions. There are two types of conditional statements in PHP: if statements and switch statements.

If Statements

We use the If statements to execute code if a certain condition is true.

The syntax of an if statement is as follows:

if (condition) {
    // code to execute
}

The code inside the curly braces will be executed if the condition is true. If the condition is false, the code will be skipped.

Switch Statements

We the Switch statements to execute code based on the value of a variable.

The syntax of a switch statement is as follows:

switch (variable) {
    case value1:
        // code to execute if variable is equal to value1
        break;
    case value2:
        // code to execute if variable is equal to value2
        break;
    default:
        // code to execute if variable is not equal to any of the values
        break;
}

Loops

We use Loops used to execute code repeatedly. In PHP, there are four types of loops: for loops, foreach loops, while loops, and do-while loops.

For Loops

We use the For loops to execute code a specific number of times.

The syntax of a for loop is as follows:

for (initialization; condition; increment) {
    // code to execute
}

The initialization statement is executed only once at the beginning of the loop. The condition is checked before each iteration of the loop. The code inside the curly braces is executed if the condition is true. After each iteration, the increment statement is executed.

Foreach Loops

We can use Foreach loops to iterate over arrays.

The syntax of a foreach loop is as follows:

foreach ($array as $value) {
    // code to execute
}

The code inside the curly braces is executed for each element in the array.

While Loops

We use While loops to execute code as long as a certain condition is true, the syntax of a while loop is as follows:

while (condition) {
    // code to execute
}

The code inside the curly braces is executed as long as the condition is true.

Do-While Loops

Do-while loops are similar to while loops, but the code inside the curly braces is executed at least once, even if the condition is false.

The syntax of a do-while loop is as follows:

do {
    // code to execute
} while (condition);

The code inside the curly braces is executed at least once, then the condition is checked. If the condition is true, the code inside the curly braces executes again.

Functions

Functions are an essential part of PHP programming. They are reusable blocks of code that perform specific tasks. Functions allow developers to write code more efficiently and make it easier to maintain.

In this section, we will discuss built-in functions and user-defined functions.

Built-in Functions

PHP comes with a wide range of built-in functions and we can use these functions to perform common tasks. These functions are already available in PHP; developers can use them without writing additional code.

Some of the most commonly used built-in functions in PHP include:

echo: Used to output text to the screen.
strlen: Used to get the length of a string.
date: Used to get the current date and time.

User-defined Functions

The developer creates user-defined functions to perform specific tasks. And they can reuse these functions throughout the application, making maintaining and updating the code easier. The function keyword is used to create a user-defined function in PHP, followed by the function name and the code block that contains the function’s instructions.

When creating user-defined functions, developers should consider the following:

Function names should be descriptive and easy to understand.
Functions should perform a single task.
Functions should have a clear purpose.

Functions are an essential part of PHP programming. They allow developers to write code more efficiently and make it easier to maintain. Built-in functions are already available in PHP and we can use them to perform common tasks. The developer can create user-defined functions to perform specific tasks and reuse them throughout the application.

Arrays

Arrays are an essential part of PHP programming. They are a collection of similar data types that store data in a single variable. Arrays are useful for storing and manipulating data in a more organized way. PHP supports three types of arrays: indexed, associative, and multidimensional.

Indexed Arrays

Indexed arrays are the simplest type of arrays in PHP. We also call them as numeric arrays because they use numeric keys to access their stored values. The first element in an indexed array has an index of 0, and the second has an index of 1, and so on. We create the Indexed arrays using square brackets [] or the array() function.

// Creating an indexed array
$fruits = ["apple", "banana", "orange"];

Associative Arrays

Associative arrays use named keys to access the values stored in them. We also call them as key-value pairs. The keys can be strings or numbers, and they must be unique. We create Associative arrays using the array() function.

// Creating an associative array
$person = array(
    "name" => "John Doe",
    "age" => 30,
    "gender" => "male"
);

Multidimensional Arrays

Multidimensional arrays are arrays that contain one or more arrays. They are useful for storing complex data structures. Multidimensional arrays can be two-dimensional, three-dimensional, or even more. We can create them using nested arrays.

// Creating a multidimensional array
$students = array(
    array("name" => "John", "age" => 20),
    array("name" => "Jane", "age" => 21),
    array("name" => "Bob", "age" => 22)
);

Arrays are an essential part of PHP programming. They are useful for storing and manipulating data in a more organized way. PHP supports three types of arrays: indexed, associative, and multidimensional.

Working with Databases

Connecting to a Database

When working with databases in PHP, the first step is establishing a connection to the database. We can do this using the mysqli_connect() function, which takes four parameters: the server name, username, password, and database name.

$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

Retrieving Data

Once we establish a connection, SQL queries can retrieve data from the database. The mysqli_query() function executes a query and returns the result set.

$sql = "SELECT * FROM customers";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // output data of each row
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 results";
}

Inserting Data

The mysqli_query() function executes an INSERT INTO query to insert data into a database.

$sql = "INSERT INTO customers (name, email, phone)
VALUES ('John Doe', 'john@example.com', '555-555-5555')";

if (mysqli_query($conn, $sql)) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

Updating Data

The mysqli_query() function executes an UPDATE query to update data in a database.

$sql = "UPDATE customers SET email='john.doe@example.com' WHERE id=1";

if (mysqli_query($conn, $sql)) {
    echo "Record updated successfully";
} else {
    echo "Error updating record: " . mysqli_error($conn);
}

Deleting Data

To delete data from a database, we use the mysqli_query() function to execute a DELETE FROM query.

$sql = "DELETE FROM customers WHERE id=1";

if (mysqli_query($conn, $sql)) {
    echo "Record deleted successfully";
} else {
    echo "Error deleting record: " . mysqli_error($conn);
}

Working with databases in PHP involves establishing a connection, executing SQL queries to retrieve, insert, update, or delete data, and handling any errors that may occur.

Object-Oriented Programming

Object-oriented programming (OOP) is a programming paradigm that uses objects to represent and manipulate data. OOP is a popular approach to software development because it promotes code reusability, modularity, and maintainability.

Click here to see our full article on Object-Oriented Programming in PHP.

Classes

PHP Classes are the building blocks of OOP. A class is a blueprint that defines the properties and methods that an object of that class will have. A class can be thought of as a user-defined data type.

Objects

A PHP object is an instance of a class. When we instantiate a class, it creates an object in memory. Objects have properties and methods that we can access and manipulate.

Inheritance

Inheritance is a mechanism that allows a class to inherit properties and methods from another class. It also promotes code reuse and helps to avoid code duplication.

Polymorphism

Polymorphism is the ability of an object to take on many forms. In OOP, we achieve polymorphism through method overriding and method overloading. Method overriding allows a subclass to implement a method already provided by its parent class. Method overloading allows a class to have multiple methods with the same name but different parameters.

Overall, OOP is a powerful programming paradigm that can help to create more modular, maintainable, and reusable code. Developers can create easier software to understand, modify, and extend using classes, objects, inheritance, and polymorphism.

Web Applications with PHP

PHP is a popular server-side scripting language widely used for web application development. With PHP, developers can create dynamic web pages, process form data, and interact with databases. In this section, we will explore some of the key features of PHP for building web applications.

HTTP Request Methods

HTTP request methods specify the type of request we make to the server. In PHP, developers can use the $_SERVER[‘REQUEST_METHOD‘] variable to determine the type of request being made.

Some of the most common HTTP request methods are:

GET: Used to retrieve data from the server
POST: Used to submit data to the server
PUT: Used to update existing data on the server
DELETE: Used to delete data from the server

Form Handling

Forms are essential to web applications, and PHP provides powerful features for handling form data. In PHP, developers can use the $_POST or $_GET variables to retrieve form data, depending on the HTTP request method. Additionally, PHP provides functions for validating form data and preventing common security vulnerabilities, such as SQL injection and cross-site scripting (XSS) attacks.

Cookies and Sessions

Cookies and sessions store data on the client-side and server-side, respectively. In PHP, developers can use the setcookie() function to set a cookie and the $_COOKIE variable to retrieve a cookie. Similarly, developers can use the session_start() function to start a session and the $_SESSION variable to store and retrieve session data.

Working with Files

File handling is another important aspect of web applications, and PHP provides a range of functions for working with files. In PHP, developers can use functions such as fopen(), fwrite(), and fclose() to read and write data to files on the server. Additionally, PHP provides functions for working with directories, such as opendir(), readdir(), and closedir().

PHP provides a powerful set of tools for building web applications. By leveraging these tools, developers can create dynamic, secure, and scalable web applications that meet the needs of their users.

Learn PHP Web Application Development: A Beginner’s Guide Summary

This article introduces beginners to PHP web application development. It covers the basics of PHP, including syntax, functions, and arrays, while emphasizing the benefits of learning PHP. The article also explores advanced topics like working with databases, object-oriented programming (OOP) concepts, and key features of PHP for web applications.

By providing a solid foundation in PHP development, the article equips beginners with the necessary skills to create dynamic websites and build web applications using PHP.

PHP Fundamentals Article Series

This article is part of our series on learning the fundamentals of PHP web development. If you are stepping into your PHP journey. Check out the articles in this series to get deeper into PHP.